This invention relates to a highly efficient, light-weight and compact refrigeration apparatus which combines four Stirling cycles to enable refrigeration to be achieved at two locations by simultaneously producing very low temperatures in the 5.degree. to 60.degree. K. range and moderately low temperatures in the 30.degree. to 200.degree. K. range.
An object of the present invention is to provide a refrigeration apparatus in which two refrigeration temperature levels produced by the apparatus can be readily extracted for utilization in order to facilitate refrigeration.
Another object of the present invention is to provide a refrigeration apparatus whose refrigerating section is reduced in size, weight and specific volume.
Still another object of the present invention is to provide a refrigeration apparatus having excellent mechanical balance.
A further object of the present invention is to provide a a refrigeration apparatus which exhibits excellent refrigerating efficiency.
According to the present invention, the foregoing and other objects are attained by providing a multiple phase Stirling cycle refrigeration apparatus in which four piston cylinders are arranged within an approximately cylindrical crankcase on a circle concentric with the crankcase. The first and third of the piston cylinders oppose each other across the center of the crankcase and produce very low temperatures, while the second and fourth of the piston cylinders similarly oppose each other across the center of the crankcase and produce moderately low temperatures. Each piston cylinder has a large diameter portion and an elongated small diameter portion and receives a similarly shaped piston adapted to be reciprocated therewithin. The small diameter portion of each piston cylinder and of the respective piston define an expansion space, and the large diameter portion of each piston cylinder and of the respective piston define a compression space on the expansion side of the large diameter portion. Means are provided for reciprocating the pistons within their respective piston cylinders in such a manner that the pistons in the first and third, and in the second and fourth, piston cylinders are displaced in phase by 180.degree.. Means interconnecting the expansion space of one piston cylinder with the compression space of the next adjacent piston cylinder include a heat exchanger and a hold-over device. The heat exchangers connected to the expansion spaces of the very low temperature piston cylinders are combined to form a very low temperature cold space disposed substantially at the center of the four piston cylinders, and the heat exchangers connected to the expansion spaces of the moderately low temperature piston cylinders are combined to form a moderately low temperature cold station disposed to surround the very low temperature cold station. In one aspect of the invention, the small diameter portions of the first and third piston cylinders and of their respective pistons are made smaller in diameter than the small diameter portions of the second and fourth piston cylinders and their respective pistons. According to a feature of the invention, the first and third piston cylinders and their associated hold-over devices are precooled by the hold-over devices or by the cold station associated with the second and fourth piston cylinders. In another aspect of the invention, the compression space of the second piston cylinder is connected to the large diameter portion of the fourth piston cylinder on the non-expansion side of the respective piston, and the compression space of the fourth piston cylinder is connected to the large diameter portion of the second piston cylinder on the non-expansion side of the respective piston, thereby to form compression spaces in the second and fourth piston cylinders on the non-expansion side of the respective pistons.
These and other objects and features of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.